The present invention is related to an improved MLCC capacitor. More specifically, the present invention is related to an improved MLCC capacitor wherein the adhesion between the MLCC and lead frame is improved.
Multi-layered ceramic capacitors (MLCC's) are widely used throughout the electronics industry. In many applications the MLCC's have leads of opposing polarity for attachment of the capacitor to a circuit. At least one MLCC is between the leads. Often multiple MLCC's are between the leads such as in a stacked arrangement. A particular problem with leaded MLCC's is their susceptibility to cracking due to a mismatch in the Coefficient of Thermal Expansion (CTE) of various components. The thermal mismatch causes stresses when subjected to temperature cycling or thermal shock. Cracking due to thermal stress has been mitigated in the prior art by methods such as the use of lead frame materials with a CTE which is less than the CTE of the MLCC, as described in U.S. Pat. No. 6,081,416, or by adding a plated flexible conductive adhesive to the MLCC, as described in U.S. Pat. No. 6,388,864.
Regardless of the advances, the art is still lacking a suitable solution to mitigate thermal stress induced cracking. In particular, the cracking which occurs due to CTE mismatches in the plating layers, which allow solder adhesion to the lead frame, are now known to be a significant source of crack propagation.